Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F8/00—Chemical modification by after-treatment
  • C08F8/42—Introducing metal atoms or metal-containing groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F259/00—Macromolecular compounds obtained by polymerising monomers on to polymers of halogen containing monomers as defined in group C08F14/00
  • C08F259/08—Macromolecular compounds obtained by polymerising monomers on to polymers of halogen containing monomers as defined in group C08F14/00 on to polymers containing fluorine
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/42—Block-or graft-polymers containing polysiloxane sequences
  • C08G77/442—Block-or graft-polymers containing polysiloxane sequences containing vinyl polymer sequences
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L51/00—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
  • C08L51/003—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers grafted on to macromolecular compounds obtained by reactions only involving unsaturated carbon-to-carbon bonds
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D183/00—Coating compositions based on macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon, with or without sulfur, nitrogen, oxygen, or carbon only; Coating compositions based on derivatives of such polymers
  • C09D183/10—Block or graft copolymers containing polysiloxane sequences

Definitions

• the present invention relates to a coating composition and more specifically to a low refractive index composition for an antireflection polymer film.
• AR films Antireflective polymer films
• AR coatings are becoming increasingly important in the display industry. New applications are being developed for low reflective films and other AR coatings applied to articles used in the computer, television, appliance, mobile phone, aerospace and automotive industries.
• AR films are typically constructed by alternating high and low refractive index polymer layers in order to minimize the amount of light that is reflected. Desirable features in AR films for use on the substrate of the articles are the combination of a low percentage of reflected light (e.g. 1.5% or lower) and durability to scratches and abrasions. These features are obtained in AR constructions by maximizing the delta RI between the polymer layers while maintaining strong adhesion between the polymer layers.
• the low refractive index polymer layers used in AR films are usually derived from fluorine containing polymers ("fluoropolymers” or “fluorinated polymers”), which have refractive indices that range from about 1.3 to 1.4.
• Fluoropolymers provide unique advantages over conventional hydrocarbon based materials in terms of high chemical inertness (in terms of acid and base resistance), dirt and stain resistance (due to low surface energy), low moisture absorption, and resistance to weather and solar conditions.
• the refractive index of fluorinated polymer coating layers is dependent upon the volume percentage of fluorine contained within the layers. Increased fluorine content decreases the refractive index of the coating layers. However, increasing the fluorine content also decreases the surface energy of the coating layers, which in turn reduces the interfacial adhesion of the fluoropolymer layer to the other polymer or substrate layers to which the layer is coupled.
• silicone-containing polymeric materials Other materials investigated for use in low refractive index layers are silicone- containing polymeric materials. Silicone-containing polymeric materials have generally low refractive indices. Further, silicone-containing polymeric coating layers generally have higher surface energies than fluoropolymer-base layers, thus allowing the silicone- containing polymeric layer to more easily adhere to other layers, such as high refractive index layers, or substrates. This added adhesion improves scratch resistance in multilayer antireflection coatings. However, silicone-containing polymeric materials have a higher refractive index as compared with fluorine containing materials. Further, silicone- containing polymeric materials have a lower viscosity that leads to defects in ultra-thin coatings (less than about 100 nanometers).
• the present invention provides a composition useful as a low refractive index layer in an antireflection coating and a method for forming the composition.
• the present invention combines the unique durability and repellency properties of fluoropolymers with the adhesion advantages of silicone-containing polymeric polymers into a single low refractive index composition.
• the present invention provides a silicone-modified fluoropolymer that is formed by first dissolving a fluoropolymer having at least one monomer of vinylidene fluoride coupled to a hexafluoropropylene monomer unit in an organic solvent and subsequently reacting the mixture with an amino silane coupling agent to form an aminosilane-modified fluoropolymer.
• the aminosilane fluoropolymer is subsequently heated and partially condensed with an oligomer of a silane compound including alkoxy silane.
• the resultant composition is ideally suited as a low refractive index layer in an AR film because the material shows good wetting to underlying or overlying materials and substrates and farther has adequate viscosity performance.
• the material is durable and relatively easy to manufacture. This material is also suited as a low refractive index layer in a transferable AR film.
• One method for application of the transferable material to a (e.g. optical) substrate is by means of a thermal application technique such as an in-mold or heat press technique.
• Figure 1 is perspective view of an article having an optical display
• Figure 2 is a sectional view of the article of Figure 1 taken along line 2-2 illustrating an antireflection film having a low refractive index layer formed in accordance with a preferred embodiment of the present invention
• Figure 3 illustrates a logic flow diagram for forming a low refractive index composition according to a preferred embodiment of the present invention.
• Figures 4-6 is a schematic illustration of a method of forming and applying a transferable antireflection material to an optical substrate according to another preferred embodiment of the present invention.
• polymer will be understood to include polymers, copolymers (e.g. polymers using two or more different monomers), oligomers and combinations thereof, as well as polymers, oligomers, or copolymers that can be formed in a miscible blend.
• low refractive index refers to the property of a composition or material, which forms a coating layer having a refractive index of less than about 1.45 when applied as a layer to a substrate.
• high refractive index refers to the property of a composition or material, which forms a coating layer having a refractive index of greater than about 1.6 when applied as a layer to a substrate.
• the difference in iiie refractive index between the low index layer and the high index layer is at least about 0.2.
• the low refractive index layer is formed having a refractive index less than a high refractive index layer.
• coating layers wherein the low refractive index layer having a refractive index slightly greater than about 1.42, when coupled with a high refractive index layer having a refractive index slightly less than about 1.6, wherein the refractive index of the low refractive index layer is less than the refractive index of the high refractive index layer, are also specifically contemplated by the present invention.
• weight ratio refers to the relative weight of the u ⁇ mpunenxs relative to each other based on the coating composition or reaction product thereof unless specified otherwise.
• percent by weight or “weight percent” refers to the weight percent solids based on the coating composition or reaction product thereof unless specified otherwise.
• the invention relates to a (e.g. transferable) antireflection material suitable for use on optical substrates.
• the optical substrate may comprise or consist of any of a wide variety of non-polymeric materials, such as glass, or various thermoplastic and crosslinked polymeric materials, such as polyethylene terephthalate (PET), (e.g. bisphenol A) polycarbonate, cellulose acetate, poly(methyl methacrylate), polyolef ⁇ ns such as biaxially oriented polypropylene which are commonly used in various optical devices.
• PET polyethylene terephthalate
• the substrate may also comprises or consist of polyamides, polyimides, phenolic resins, polystyrene, styrene-acrylonitrile copolymers, epoxies, and the like.
• the substrate will be chosen based in part on the desired optical and mechanical properties for the intended use. Such mechanical properties typically will include flexibility, dimensional stability and impact resistance.
• the substrate thickness typically also will depend on the intended use. For most applications, substrate thicknesses of less than about 0.5 mm are preferred, and more preferably about 0.02 to about 0.2 mm.
• Self- supporting polymeric films are preferred.
• the polymeric material can be formed into a film using conventional filmmaking techniques such as by extrusion and optional uniaxial or biaxial orientation of the extruded film.
• the substrate can be treated to improve adhesion between the substrate and the hardcoat layer, e.g., chemical treatment, corona treatment such as air or nitrogen corona, plasma, flame, or actinic radiation. If desired, an optional tie layer or primer can be applied to the substrate and/or hardcoat layer to increase the interlayer adhesion.
• the substrate is light transmissive, meaning light can be transmitted through the substrate such that the display can be viewed.
• Various light transmissive optical film are known including but not limited to, multilayer optical films, microstructured films such as retroreflective sheeting and brightness enhancing films, (e.g. reflective or absorbing) polarizing films, diffusive films, as well as (e.g. biaxial) retarder films and compensator films such as described in U.S. Patent Application Publication No. 2004/0184150, filed January 29, 2004.
• multilayer optical films i.e., films that provide desirable transmission and/or reflection properties at least partially by an arrangement of microlayers of differing refractive index.
• the microlayers have different refractive index characteristics so that some light is reflected at interfaces between adjacent microlayers.
• the microlayers are sufficiently thin so that light reflected at a plurality of the interfaces undergoes constructive or destructive interference in order to give the film body the desired reflective or transmissive properties.
• each microlayer generally has an optical thickness (i.e., a physical thickness multiplied by refractive index) of less than about 1 ⁇ m.
• thicker layers can also be included, such as skin layers at the outer surfaces of the film, or protective boundary layers disposed within the film that separate packets of microlayers.
• Multilayer optical film bodies can also comprise one or more thick adhesive layers to bond two or more sheets of multilayer optical film in a laminate.
• the reflective and transmissive properties of multilayer optical film body are a function of the refractive indices of the respective microlayers.
• Each microlayer can be characterized at least at localized positions in the film by in-plane refractive indices n x , n y , and a refractive index n z associated with a thickness axis of the film. These indices represent the refractive index of the subject material for light polarized along mutually orthogonal x-, y-, and z-axes.
• the refractive indices are controlled by judicious materials selection and processing conditions.
• Films can be made by co-extrusion of typically tens or hundreds of layers of two alternating polymers A 5 B, followed by optionally passing the multilayer extrudate through one or more multiplication die, and then stretching or otherwise orienting the extrudate to form a final film.
• the resulting film is composed of typically tens or hundreds of individual microlayers whose thicknesses and refractive indices are tailored to provide one or more reflection bands in desired region(s) of the spectrum, such as in the visible or near infrared.
• adjacent microlayers preferably exhibit a difference in refractive index ( ⁇ n x ) for light polarized along the x-axis of at least 0.05.
• the adjacent microlayers also preferably exhibit a difference in refractive index ( ⁇ %) for light polarized along the y-axis of at least 0.05. Otherwise, the refractive index difference can be less than 0.05 and preferably about 0 to produce a multilayer stack that reflects normally incident light of one polarization state and transmits normally incident light of an orthogonal polarization state. If desired, the refractive index difference ( ⁇ n z ) between adjacent microlayers for light polarized along the z-axis can also be tailored to achieve desirable reflectivity properties for the p-polarization component of obliquely incident light.
• Exemplary materials that can be used in the fabrication of polymeric multilayer optical film can be found in PCT Publication WO 99/36248 (Neavin et al.).
• at least one of the materials is a polymer with a stress optical coefficient having a large absolute value.
• the polymer preferably develops a large birefringence (at least about 0.05, more preferably at least about 0.1 or even 0.2) when stretched.
• the birefringence can be developed between two orthogonal directions in the plane of the film, between one or more in-plane directions and the direction perpendicular to the film plane, or a combination of these.
• the preference for large birefringence in at least one of the polymers can be relaxed, although birefringence is still often desirable.
• Such special cases may arise in the selection of polymers for mirror films and for polarizer films formed using a biaxial process, which draws the film in two orthogonal in-plane directions.
• the polymer desirably is capable of maintaining birefringence after stretching, so that the desired optical properties are imparted to the finished film.
• a second polymer can be chosen for other layers of the multilayer film so that in the finished film the refractive index of the second polymer, in at least one direction, differs significantly from the index of refraction of the first polymer in the same direction.
• the films can be fabricated using only two distinct polymer materials, and interleaving those materials during the extrusion process to produce alternating layers A, B, A, B, etc. Interleaving only two distinct polymer materials is not required, however.
• each layer of a multilayer optical film can be composed of a unique material or blend not found elsewhere in the film.
• polymers being coextruded have the same or similar melt temperatures.
• Exemplary two-polymer combinations that provide both adequate refractive index differences and adequate inter-layer adhesion include: (1) for polarizing multilayer optical film made using a process with predominantly uniaxial stretching, PEN/coPEN, PET/coPET, PEN/sPS, PET/sPS, PEN/Eastar,.TM. and PET/Eastar,.TM.
• PEN refers to polyethylene naphthalate
• coPEN refers to a copolymer or blend based upon naphthalene dicarboxylic acid
• PET refers to polyethylene terephthalate
• coPET refers to a copolymer or blend based upon terephthalic acid
• sPS syndiotactic polystyrene and its derivatives
• EastarTM is a polyester or copolyester (believed to comprise cyclohexanedimethylene diol units and terephthalate units) commercially available from Eastman Chemical Co.; (2) for polarizing multilayer optical film made by manipulating the process conditions of a biaxial stretching process, PEN/coPEN, PEN/PET, PEN/PBT, PEN/PETG and PEN/PETcoPBT, where "PBT” refers to polybutylene terephthalate, "PETG” refers to a copolymer of PET employing
• PET/PMMA PET/PMMA, PEN/EcdelTM, PET/EcdelTM, PEN/sPS, PET/sPS, PEN/coPET, PEN/PETG, and PEN/THVTM, where "PMMA” refers to polymethyl methacrylate
• EcdelTM is a thermoplastic polyester or copolyester (believed to comprise cyclohexanedicarboxylate units, polytetramethylene ether glycol units, and cyclohexanedimethanol units) commercially available from Eastman Chemical Co.
• THVTM is a fluoropolymer commercially available from 3M Company.
• polymeric multilayer optical films and film bodies can comprise additional layers and coatings selected for their optical, mechanical, and/or chemical properties. See U.S. Pat. No. 6,368,699 (Gilbert et al.).
• the polymeric films and film bodies can also comprise inorganic layers, such as metal or metal oxide coatings or layers.
• the surface energy can be characterized by various methods such as contact angle and ink repellency, as determined by the test methods described in the examples.
• the surface layer and articles described preferably exhibit a static contact angle with water of at least 70 degrees. More preferably, the contact angle is at least 80 degrees and more preferably at least 90 degrees. Alternatively, or in addition thereto, the advancing contact angle with hexadecane is at least 50 degrees and more preferably at least 60 degrees.
• Low surface energy is indicative of anti-soiling properties as well as rendering the exposed surface cdby iu clean. Another indicator of low surface energy relates to the amount of ink from a pen or marker, which beads up when applied to the exposed surface.
• the surface layer and articles exhibit "ink repellency" when the ink from pens and markers can be easily removed by wiping the exposed surface with a tissues or paper towels, such as tissues available from the Kimberly Clark Corporation, Roswell, GA under the trade designation "SURPASS FACIAL TISSUE.”
• optical display or "display panel” include various illuminated and non- illuminated displays panels.
• Such displays include multi-character and especially multicharacter, multi-line displays such as liquid crystal displays (“LCDs”), plasma displays, front and rear projection displays, cathode ray tubes (“CRTs”), signage, as well as single- character or binary displays such as light emitting tubes (“LEDs”), signal lamps and switches.
• the light transmissive (i.e. exposed surface) substrate of such display panels may be referred to as a "lens.”
• the invention is particularly useful for displays having a viewing surface that is susceptible to damage.
• the coating composition, reactive product thereof, as well as the protective articles of the invention can be employed in a variety of portable and non-portable information display devices including PDAs, cell phones (including combination PDA/cell phones), touch sensitive screens, wrist watches, car navigation systems, global positioning systems, depth finders, calculators, electronic books, CD and DVD players, projection televisions screens, computer monitors, notebook computer displays, instrument gauges, instrument panel covers, signage such as graphic displays and the like.
• PDAs portable and non-portable information display devices
• cell phones including combination PDA/cell phones
• touch sensitive screens touch sensitive screens
• wrist watches car navigation systems, global positioning systems, depth finders, calculators, electronic books, CD and DVD players
• projection televisions screens computer monitors
• notebook computer displays notebook computer displays
• instrument gauges instrument panel covers
• signage such as graphic displays and the like.
• the coating composition, reactive product thereof, as well as the protective articles of the invention can be employed on a variety of other articles as well such as, for example, camera lenses, eyeglass lenses, binocular lenses, retroreflective sheeting, automobile windows, building windows, train windows, aircraft windows, vehicle headlamp and taillights, and the like.
• camera lenses, eyeglass lenses, binocular lenses, retroreflective sheeting automobile windows, building windows, train windows, aircraft windows, vehicle headlamp and taillights, and the like.
• FIG. 1 a perspective view of an article, here a computer monitor 10, is illustrated as having an optical display 12 coupled within a housing 14.
• the optical display 12 is a substantially transparent material having optically enhancing properties through which a user can view text, graphics or other displayed information.
• the optical display 12 includes an antireflection film 18 coupled (coated) to an optical substrate 16.
• the antireflection film 18 has at least one layer of a high refraction index layer 22 and a low refractive index layer 20 coupled together such that the low refractive index layer 20 is exposed to the atmosphere while the high refractive index layer 22 is contained between the substrate 16 and low refractive index layer 20.
• the high refractive index layer 22 is a conventional carbon-based polymeric composition having a mono and multifunctional acrylate crosslinking system. Exemplary non-limiting high refractive index compositions that may be utilized to form the high refractive index layer 22 in the present invention are described in U.S. Patent No.
• the low refraction index layer 20 is designed to be compatible with the high refractive index layer 22 and is formed from the reaction product an oligomer of a silicone alkoxy resin partially condensed with an aminosilane modified fluoropolymer.
• the method for forming the low refractive index layer 20 is described in further detail below.
• Articles with which the present invention can be utilized include, for example, lenses, cathode ray tubes, flat or curved panel displays, window films and windshields. It is understood, of course, that the present invention is not limited to such articles, but can be utilized with any articles within the skill of persons in the art.
• the substrate 16 While not shown, other layers may be added onto the substrate 16, including, but not limited to, other hard coating layers, adhesive layers, and the like. These layers are formed with conventional hydrocarbon-based compositions that are designed to be compatible with the overlying layers of the antireflection material 18.
• the antireflection material 18 may be applied directly to the substrate 16, or alternatively applied to a release layer of a transferable antireflection film and subsequently transferred from the release layer to the substrate using a heat press or photoradiation application technique.
• Figure 3 illustrates a logic flow diagram for forming the low refraction index coating composition used m the low refractive index coating layer 20 of Figure 1 in accordance with one preferred method of the present invention.
• a fluoropolymer is first dissolved in a compatible organic solvent.
• the solution is about 10% by weight fluoropolymer and 90% by weight organic solvent.
• the preferred fluoropolymer is a copolymer that is formed from the constituent monomers known as (poly)tetrafluoroethylene (“TFE” or “PTFE”), hexafluoropropylene (“HFP”), and (poly)vinylidene fluoride (“VdF 5 " "V 2 F,” or “PVdF”).
• TFE polytetrafluoroethylene
• HFP hexafluoropropylene
• VdF 5 polyvinylidene fluoride
• the fluoropolymer copolymer consists of at least two of the constituent monomers (HFP and VdF), and more preferably all three of the constituent monomers in varying molar amounts.
• THV a copolymer of all three fluoropolymers
• FKM a copolymer consisting of HFP and VdF
• THV contemplated for use in the present invention is DyneonTM Fluorothermoplastic THV 220, a mixture that is manufactured by 3M of Saint Paul, Minnesota.
• FKM Fluorothermoplastic THV 220
• FKM DuPont's Dow Elastomer Viton® A-201C.
• Useful fluoropolymers are also commercially available, for example from Dyneon LLC, Saint Paul Minn., under the trade names THV 230, THV 500, THV530, FluorelTM (HFP/VDF), Fluorel-IITM (TFE/PP /VDF), and Kel-F.TM.
• KF-800, fiuoroelastomer from Elf Atochem North America Inc., under the trade names KynarTM 740, 2800, 9301; from Kureha Chemical Co. under the trade name KF polymer; from Daikin Amciiua, Inc. under the trade name NEOFLUORON VDF; from Central Glass under the trade name Cefral SoftTM G-150, from Asahi Glass Co., Ltd., under the trade name AFLASTM 200; and from DuPont under the tradename Dow Elastomer Viton® A- 201C.
• the compatible organic solvent that is utilized in the preferred embodiments of the present invention is methyl ethyl ketone ("MEK”).
• MEK methyl ethyl ketone
• other organic solvents may also be utilized, as well as mixtures of compatible organic solvents, and still fall within the spirit of the present invention.
• other organic solvents contemplated include methyl isobutyl ketone (“MIBK”), methyl amyl ketone (“MAK”), tetrahydrofuran (“THF”), isopropyl alcohol (“IPA”), and mixtures thereof.
• the mechanical durability of the resultant low retractive index layer 20 can be enhanced by the introduction of surface modified inorganic particles to the low refractive index composition.
• the inorganic particles preferably have a substantially monodisperse size distribution or a polymodal distribution obtained by blending two or more substantially monodisperse distributions.
• the inorganic oxide particles are typically non-aggregated (substantially discrete), as aggregation can result in precipitation of the inorganic oxide particles or gelation of the hardcoat.
• the inorganic oxide particles are typically colloidal in size, having an average particle diameter of 5 nanometers to 100 nanometers. These size ranges facilitate dispersion of the inorganic oxide particles into the binder resin and provide ceramers with desirable surface properties and optical clarity.
• the average particle size of the inorganic oxide particles can be measured using transmission electron microscopy to count the number of inorganic oxide particles of a given diameter.
• Inorganic oxide particles include colloidal silica, colloidal titania, colloidal alumina, colloidal zirconia, colloidal vanadia, colloidal chromia, colloidal iron oxide, colloidal antimony oxide, colloidal tin oxide, and mixtures thereof. Most preferably, the particles are formed of silicone dioxide (SiO 2 ).
• the surface particles are modified with polymer coatings designed to have reactive functionality towards the fluoropolymer component of the fluoropolymer phase.
• Such functionalities include mercapotan, vinyl, acrylate and others believed to enhance the interaction between the inorganic particles and low index fluoropolymers, especially those containing bromo or iodo cure site monomers.
• the surface modifications allow further Ciussii ⁇ king of 'the particle within the polymer network and allow adequate dispersion of the particles in the fluoropolymer matrix.
• a solution of amino silane coupling agent is added to the fluoropolymer solution.
• One preferred amino silane coupling agent is 3-aminopropyl methoxy silane:
• the reaction mechanism for forming the aminosilane modified fluoropolymer preferentially and substantially occurs at vinylidene fluoride groups that are located next to HFP groups in the THV or FKM molecules.
• the reaction mechanism is a dehydrofluorination reaction of the VdF group followed by Michael addition reaction and is described chemically below (for illustrative purposes, 3-aminopropyl methoxy silane is utilized as the amino silane coupling agent):
• the reaction is limited by the number of VdF groups coupled to the HFP groups contained in the fluoropolymer. As a result, excess amino silane coupling agent in solution has little, if any, additional chemical effect.
• the amino silane coupling agent is added in a range of between about 5 and 10 weight percent of the total mixture.
• Step 120 the aminosilane modified fluoropolymer solution is placed into a container and reacted with an oligomer of a silane compound having the chemical formula:
• Si-(ORl) ra R2 n wherein ⁇ ? 1 o r ⁇ g_2 are alkyl groups, m in a whole number between 1 and 4, n is a whole number between 0 and 3, and wherein the sum of m and n is 4.
• Two preferred oligomers that meet these criteria are organic alkoxy silanes and tetraalkoxy silanes.
• a portion of the Rl alkyl may be replaced by an acetyl group.
• the oligomer of a silane compound is a mixture of organic alkoxy silane and tetraalkoxy silane, with the preferred weight ratio of tetraalkoxy silane to organic alkoxy silane in the resultant composition being between about 2: 1 and 3:1.
• the solids of the mixture are ideally adjusted to between about 2 and 10 weight percent, using a compatible organic solvent that quenches the reaction, and more desirably between about 8 and 10 weight percent.
• One preferred solvent to quench the reaction and prevent gelation is THF.
• a higher boiling point solvent such as propylene glycol monomethyl ether acetate ("PMA"), is preferably added as a portion of the solvent package.
• PMA propylene glycol monomethyl ether acetate
• the container containing the mixture is placed in a heated water bath for between about 1 and 4 hours at between 60 and 80 degrees Celsius in order that the pendent silicone methoxy groups of the amino-silane modified fluoropolymer solution react, via a condensation reaction, with the alkoxy silane portion of the organic alkoxy silane or tetra alkoxy silane.
• the reaction mechanism for first forming the resultant product, a silicone modified fluoropolymer, mixed with tetramethoxy silane (the tetraalkoxy silane oligomer) and alkyl-trimethoxy silane (the organic alkoxy silane oligomer) is shown below:
• the resultant product a silicone modified fluoropolymer
• the addition of the solvent in essence, quenches the reaction, therein preventing further reaction to prevent gelation of the product.
• THF is the preferred solvent for quenching the resultant product, but exhibits too fast a drying rate to be used in a thin coating. Therefore, it is preferable to utilize a mixture of THF with another compatible high boiling point solvent such as cyclohexanone and MIBK, the mixture amounts depending upon the desired drying rate for the applied coating.
• a stabilizing agent such as dibutyltin dilaurate is also added to the final mixture. This stabilizing agent complexes with some of the remaining alkoxy silane in the resultant product.
• the stabilizing agent is typically added at between about 1 and 3 weight percent of the thinned solution.
• the resultant composition is ideally suited as a low refractive index layer because the material shows good wetting to underlying or overlying materials and substrates and further has adequate viscosity performance.
• the material is easy to manufacture because of its relatively simple synthesis procedure.
• Transferable antireflection material can be applied, after formation, to the substrate by various techniques.
• the transferable antireflection material is applied with a radiation curing technique as described in U.S. Application No. 11/027655, filed Dec. 30, 2004.
• An alternative technique is a thermal application technique such as a heat transfer method or in-mold transfer process, as described below in Figures 4-6.
• Figures 4 and 5 below illustrate two methods for forming an optical display via a thermal application technique.
• the process for either technique begins by first providing the transferable antireflection film 30.
• the deviation in either process involves the subsequent application of the transferable film to the optical substrate 42.
• the antireflection coating layers 34 are first applied, one layer at a time, to a temporary transferring material known as a release layer 32.
• the release layer 32 is preferably a material that is capable of adhering any layer of coaling applied xo it for storage and transport.
• the release layer 32 also has a stable transfer performance of the antireflection material 34 to the substrate 42 during the subsequent application stage.
• One preferred release layer meeting these requirements is polyethylene terephthalate film, or PET film, having a thickness of about 25-75 microns.
• a wet layer of low refractive index 36 is applied to the release layer 32 using a Mayer bar or similar device. This wet layer 36 is then dried in an oven to a preferred dry thickness of about 75- 100 nanometers.
• the low index reflection layer 36 is preferably the previously described silicone- modified fluoropolymer material having good durability and low refractivity.
• the layer 16 also has appropriate adhesion to the release layer 32 and adequate adhesion to the later- applied high index refraction layer 38.
• a wet layer of a high index refraction material is applied to the dried low refraction index layer 36 using a Mayer bar or similar device.
• the high index material is dried in an oven and irradiated with an ultraviolet light source from the PET film 32 side to form a high index layer 38 having a thickness of about 100-125 nanometers.
• the main component of the high index matrix resin is a monomer or an oligomer having one or more ultraviolet light (“UV”) curable double bonds in order that the resultant layer 38 formed has sufficient cohesion force (by high cross-linking density). Due to reaction speed, acrylic monomers or oligomers are desirable for use as the high index matrix resin.
• UV ultraviolet light
• multi-functional monomers or oligomers are also utilized as a portion of the matrix resin.
• Two preferred multi-functional acrylates that are utilized are Dipentaerithriotal penta/hexaacrylate (DPHA) and pentaerithritol tri/tetra acrylate (PETA).
• DPHA Dipentaerithriotal penta/hexaacrylate
• PETA pentaerithritol tri/tetra acrylate
• a multi-functional epoxy acrylate as a portion of the matrix resin to improve scratch resistance performance.
• Two preferred multifunctional epoxy acrylates that may be used are Bisphenol A epoxy acrylate and Cresol novolac epoxy acrylate.
• Zirconium dioxide (“ZrO 2 ”) and titanium dioxide (“TiO 2 ”) are desirable particles for use in high index refractive layers 38.
• the particle size of the high index inorganic particles is preferably less than about 50 nm in order that it is sufficiently transparent.
• ITO indium tin oxide
• ATO antimony tin oxide
• These high index particles are first mixed with an organic solvent by using common organosol preparation methods. One example is to prepare a sol in water and then replace the water slowly with organic solvent. Another example is to first disperse the dried particles in organic solvents. In one embodiment, dried rutile fine TiO 2 particles are dispersed with dispersant in an organic solvent using a sand mill. The particles are then introduced to the matrix resin to form the high index composition for the layer 38.
• the composition of the high refractive layer 38 includes alkoxy silyl groups.
• a silane coupling agent in the component of the high index layer. Since the high index layer is preferably an acrylates bond material, silane coupling agent with acrylic functional group is preferably utilized.
• the reaction mechanism for forming the ammosilane modified fluoropolymer preferentially and substantially occurs at vinylidene fluoride groups that are located next to HFP groups in the THV or FKM molecules.
• the reaction mechanism is a dehydrofluorination reaction of the VdF group followed by an Michael addition reaction.
• the low refractive index layer 36 mentioned above also includes alkoxy silyl groups, siloxane bonding will occur at the layer interface when the high index layer 38 is cured. These siloxane bonds are believed to improve scratch resistance of the transferable material 30 after application to the substrate 42.
• UV irradiation of more than 300 nm should be utilized to prevent the low index layer 36 from increasing adhesion to the PET release layer 32 to undesirable levels, therein adversely affecting the subsequent release performance of the release layer 32.
• UV exposure of the high index layer 38 is preferably done from the PET side 32 to filter off the short UV light ranges. Since this high index layer 38 is very thin, typically around 100 nm, it is also desirable to irradiate the layer under an inert gas atmosphere to substantially prevent oxygen free radical damage that may occur.
• alcohol solvents are desirable considering the surface tension and solubility of the low index layer 36.
• other organic solvents such as methyl ethyl ketone (“MEK”) and butyl cellosolve can also be used.
• a wet layer of a hard coating material such as layer 40 is applied to the high refractive index layer 38 using a Mayer bar or similar device.
• the hard coating film is dried in an oven and exposed to an ultraviolet light source, from the PET film 12 side. This forms a hard coating layer having a thickness of about 5 microns.
• a corona discharge treatment is next optionally and preferably applied to the exposed surface of the hard coat layer 40.
• the purpose of the hard coating layer 40 is to prevent scratching.
• the scratch resistance of the layer is dependent upon the crosslinking density of the hard coating layer
• the adhesion of the hard coat layer 40 to the high refractive index layer 38 is partially dependent upon the compatibility of the hard coating layer 40 to the high index refraction layer 38.
• a desirable hard coating composition for use in the present invention is an acrylic UV curable system that increases the interfacial adhesion to the overlying acrylic high refractive index layer 38.
• the use of a multifunctional acrylic monomer and a multifunctional polyurethane acrylate is desirable.
• difunctional acrylate resins are preferred over trifunctional or higher order acrylate resins.
• an adhesive material 41 such as layer 41, is applied to the hard coating layer 40 using a Mayer bar or similar device and dried in an oven to form an adhesive layer.
• the corona discharge treatment previously applied to the hard coating layer 40 acts to increase the interfacial adhesion between the hard coating layer 40 and the adhesive layer
• the adhesive layer 41 has a thickness of about 2 micrometers.
• the adhesive layer 41 is chosen based on its affinity with the substrate material 22 and hard coating layer 40 to which it is applied. Copolymers of polyvinyl chloride/poly vinyl acetate and acrylic polymers are preferably used for this purpose.
• the transferable antireflection layer 30 of Figures 2 and 3 is fully formed and is stored until needed.
• One method of thermally coupling the transferable antireflection material comprises providing a mold having a bottom plate and a top plate; introducing the optical substrate and said transferable antireflection material such that said adhesive layer is closely coupled to the optical substrate; heating the top and bottom plate; closing the mold thereby adhering the adhesive layer to the optical substrate; opening the mold; and removing the optical device from the mold.
• the transferable antireflection layer 30 and optical substrate 42 are placed into a heat mold 46, with the adhesive layer 41 being closely coupled to the substrate 42.
• the mold 46 is then closed.
• a heated upper plate 48 is pressed at a first pressure onto the release layer 42, while a heated lower plate 50 is pressed in the opposite direction onto the substrate 42 for a predetermined amount of time sufficient to adhere the adhesive layer 41 to the substrate 42.
• the mold 46 is then opened, and the optical substrate having the coupled transferable layer 30 is removed and cooled.
• the release layer 32 is peeled away from the low refraction index layer 36. The result is a transferable antireflection film 30 being applied to the optical substrate 42.
• the transferable antireflection film 30 can be applied to an optical substrate 42 as the optical substrate is being formed via an in-mold transfer process as described below in Figures 3-5.
• Such method may comprise introducing the transferable antireflection material within an inner cavity of a molding die; closing the molding die; injecting a quantity of a molten polymeric material to substantially fill the inner cavity, cooling the molten polymeric material; removing the optical substrate having the applied transferable antireflection material from the molding die; and removing the release layer from the low refractive index layer.
• the transferable antireflection film 30 is first placed within an injection mold 73 between a first piece 75 and a second piece 77.
• the release layer 32 is closely coupled to the second piece 77 and away from the first piece 75.
• the mold 73 is closed, as shown in Figure 4, and the transferable film 30 is contained within a cavity 71 defined by the inner surfaces 79, 81 of the first piece 75 and second piece 77, respectively.
• a quantity of molten optical substrate polymeric material 83 is introduced (i.e. injected) through an opening 85 within the first piece 75 at a predetermined temperature and pressure.
• the molten material 83 fills the cavity 71 and causes the transferable film 10 to be pressed against the inner surface 81 of the second piece 77.
• the molten material 79 is then cooled to form the optical substrate 42.
• the interaction between the adhesive layer 41 and cooled substrate 42 creates adhesion to couple the transferable antireflection film 30 to the formed substrate.
• the mold 73 is opened, and the optical substrate and transferable film 30 are removed from the cavity 71.
• the release layer 32 is then peeled away from the low refraction index layer 36, leaving the formed optical display.
• the present transferable antireflection material offers several advantages. First, the material does not have strong adhesion to the PET film, so stable transfer is achieved without an additional release layer. Second, the high index refraction layer is stably constructed on the low index layer without causing a dewetting problem. Third, because the low index refraction layer includes numerous functional groups to form siloxane bonds, the resultant material achieves high durability. Fourth, the low index refraction layer is porous enough to allow the high index refraction layer to partially penetrate upon application, therein improving adhesion between the layers, which results in improved scratch resistant in the overall coating layer.
• compositions including a silicone material modified fluoropolymer, were prepared.
• THV 220 (Dyneon) were dissolved in MEK and 4Og of a 10 weight percent solution was prepared.
• the solution was allowed to sit in an airtight container for 10 days under ambient conditions. After 10 days, the solution, known as a modified polymer solution, was slightly yellow.
• the solids percentage was about 1.5 weight percent and the weight ratio of THV 220 to oligomerized amino silane coupling agent was 90/10.
• 400g of the modified polymer solution, 72g of an organic alkoxy silane oligomer (SI oligomer 2, GE Toshiba silicone), 5Og of an oligo tetra methoxy silane (X40-2308, Shinetsu chemical), 24g of THF and 54g of PMA were mixed in a container.
• the mixture was then coated onto a PET substrate material using a Mayer bar, and the resultant coating showed a very hazy appearance.
• L-I, L-2, and L-3 were coated on 75 um PET film substrate material with Mayer bar and dried to a target thickness of about 110 nm.
• four samples of commercially available materials were also prepared and applied to a 75 um PET film substrate ni ⁇ ieii ⁇ ai a similar thickness (between 95 and 110 nm) and evaluated versus L-I, L-2 and L-3.
• FT-2430 (Dyneon) is first dissolved in MEK and 400g of a 10 weight percent solution was prepared.
• 1001.4g of THF and 2.1 Ig of amino silane coupling agsnt (KBM-903, Sl ⁇ cisu Chemical) were added and mixed.
• the resultant solution was allowed to sit in an airtight container for 10 days under ambient conditions. After 10 days, the resultant solution was a little yellow.
• the solids percentage was 3.0 weight percent and the weight ratio of FT-2430/KBM-903 was about 95/5.
• TFE Tetrafluoroethylene
• HFP Hexafluoropropylene
• VdF Vinylidenefluoride
• MEK Methyl Ethyl Ketone
• Solution Lt-3 was a commercially available solution of UV curable fluorinated acrylic compound (Product name: TMOl 1, JSR) diluted with Methyl Isobutyl Ketone (MIBK) to 1.5 weight percent solids.
• TMOl 1, JSR UV curable fluorinated acrylic compound
• MIBK Methyl Isobutyl Ketone
• Solution Lt-4 was a commercially available oligo organo silane material (Product name: SI oligomer 2, GE Toshiba Silicone) diluted with to 2.0 weight percent solids in IPA.
• TiO2 dispersion 50Og Of TiO 2 particles with Rutile structure (Product name: TTO-V-3, Ishihara), 25Og of dispersant (Product name: Disperbyk 2000, BYK Chernie), 104Og of IPA, and 21Og of Butyl Cellosolve were mixed well to obtain a TiO 2 dispersion. The solids percentage of the dispersion was adjusted to 22.1 weight percent.
• Preparation of oligomer of silane coupling agent (5103 Hv) 50Og Of TiO 2 particles with Rutile structure (Product name: TTO-V-3, Ishihara), 25Og of dispersant (Product name: Disperbyk 2000, BYK Chernie), 104Og of IPA, and 21Og of Butyl Cellosolve were mixed well to obtain a TiO 2 dispersion. The solids percentage of the dispersion was adjusted to 22.1 weight percent.
• Ig ⁇ f ihe TiO2 dispersion described above was mixed in a glass bottle with 13.92g of IPA, 1.4g of MEK, 0.87g of Butyl Cellosolve, and the mixture was treated with ultrasonic agitation for 5 minutes.
• Pentaerythritol tri/tetra acrylate (Product name: NK ester A-TMM-3, ShinNakamura chemical), 0.26g of 5103Hy described above, 0.18g of a 5 weight percent solution of photo-initiator (Product name: Irgacure 369, Ciba specialty chemical) in MEK and 0.18g of a 5 weight percent solution of Di-butyltin dilaurate in MEK.
• the resultant mixture was stirred and the solids adjusted to 2.6 weight percent.
• Ig of a TiO 2 dispersion described above was mixed in a glass bottle with 13.92g of IPA, 1.4g of MEK, 0.87g of Butyl Cellosolve, and the mixture was treated with ultrasonic agitation for 5 minutes.
• To this mixture was added 2.44g of Novolac epoxy acrylate (Product name: NK oligo EA-7420, ShinNakamura Chemical), 0.26g of 5103Hy described above, 0.18g of a 5 weight percent solution of photo-initiator (Product name: Irgacure 369, Ciba Specialty Chemical) in MEK and 0.18g of a 5 weight percent solution of Di-butyltin dilaurate in MEK. The resultant mixture was stirred and the solids percentage was adjusted to 2.6 weight percent.
• Example 1 On 75 um PET (Product name: 0-75, Teijin), L-I described above was coated by Mayer bar #6 and dried in 80 0 C oven for 30 seconds and then put in 12O 0 C oven for 20 seconds to make a low index layer with approximately 90 run thickness.
• H-I On the low index layer, H-I was coated by Mayer bar #8 and dried in 80 0 C oven for 30 seconds and then put in 120 0 C oven for 20 seconds.
• the H-I coated film was UV exposed for 8 seconds from the PET release layer side with a 120 W Fusion lump (D bulb) under nitrogen gas atmosphere to make a high index layer with approximately 130 run thickness.
• HC-I was coated by Mayer bar #10 and dried in 80°C oven for 60 seconds.
• This coated film was UV exposed for 8 seconds from the PET release layer side with a 120 W Fusion lump (D bulb) under N2 atmosphere to make hard coating layer with approximately 5 um thickness.
• Adh-1 was coated by Mayer bar #9 and dried in 8O 0 C oven for 60 seconds to make adhesive layer with approximately 2 um thickness and then transferable AR material named TAR-I was completed.
• TAR-I and a commercial acrylic board with 7 cm square and 2 mm thickness were put together and inserted into a heat-press machine with two metal plates and heat-pressed for 40 seconds with 30 MPa pressure. The temperatures of the plates were 180 0 C for film/acrylic side and 50°C for the opposite side. The pressed materials were taken out and PET film was removed after cooling. As a result, the anti- reflection layer was successfully transferred on the acrylic surface.
• Example 2 TAR-I in Example 1 was inserted into a molding die and PMMA was injection molded with 24O 0 C injection temperature. The pressed materials were taken out and PET film was removed after cooling. As a result, the anti-reflection layer was successfully transferred on the molding surface.
• Example 3 The same procedure was taken to make TAR-2 except using H-3 in
• TAR-2 and a commercial acrylic board with 7 cm square and 2 mm thickness were put together and inserted into a heat-press machine with two metal plates and heat-pressed for 40 seconds with 30 MPa pressure.
• the temperatures of the plates were 180 0 C for film/acrylic side and 50°C for the opposite side.
• the pressed materials were taken out and PET film was removed after cooling. As a result, the anti- reflection layer was successfully transferred on the acrylic surface.
• Example 4 The same procedure was taken to make TAR-3 except using H-4 for H-I in Example 1.
• TAR-3 and a commercial acrylic board with 7 cm square and 2 mm ihickness were put together and inserted into a heat-press machine with two metal plates and heat-pressed for 40 seconds with 30 MPa pressure.
• the temperatures of the plates were 180 0 C for film/acrylic side and 50°C for the opposite side.
• the pressed materials were taken out and PET film was removed after cooling. As a result, the anti- reflection layer was successfully transferred on the acrylic surface.
• Comparison Example T-I The same procedure was employed as Example 1 except using Lt-2 in place of Lt- 1.
• this transferable AR material and commercial acrylic sheet with 7 cm square and 2 mm thickness were put together and were inserted into a heat-press machine with two metal plate and heat-pressed for 40 seconds with 30 MPa pressure.
• the temperatures of the plates were 180°C for film/acrylic side and 50°C for the opposite side.
• the pressed materials were taken out and PET film was removed after cooling.
• the breaking portion was the interface of low index layer and high index layer and antireflection material transfer failed. The reason for the failure was attributed to too much adhesion of the low index layer to the PET release layer.
• Comparison Example T-2 The same procedure was employed as Example 1 except using Lt-4 in place of Lt- 1.
• this transferable AR material and commercial acrylic sheet with 7 cm square and 2 mm thickness were put together and were inserted into a heat-press machine with two metal plates and heat-pressed for 40 seconds with 30 MPa pressure.
• the temperatures of the plates were 180 0 C for film/acrylic side and 50 0 C for the opposite side.
• the pressed materials were taken out and PET film was removed after cooling.
• the breaking portion was the interface of low index layer and high index layer and antireflection material transfer failed. The reason for the failure was attributed to too much adhesion of the low index layer to the PET release layer.
• Comparison Example T-3 On 75 um PET (Product name: 0-75, Teijin), Lt-3 described above was coated by Mayer bar #6 and dried in 80 0 C oven for 30 seconds and then put in 12O 0 C oven for 20 seconds to make low index layer with approximately 90 nm thickness. On the low index layer, H-I was coated by Mayer bar #8 and dried in 80 0 C oven for 30 seconds, however during drying, the organic solvent in high index layer dissolved the low index layer. As a result, some surface imperfection (pattern) was observed on the high index layer and the experiment was suspended.
• Comparison Example T-4 On 75 um PET (Product name: 0-75, Teijin), Lt-3 described above was coated by Mayer bar #6 and dried in 8O 0 C oven for 30 seconds and then put in 12O 0 C oven for 20 seconds. This coated film was UV exposed for 8 seconds from the PET side with a 120 W Fusion lump (D bulb) under nitrogen gas atmosphere to make low index layer with a thickness of approximately 90 nm. However, when high index layer solution was coated on the low index layer, severe dewetting phenomenon was observed and high index layer was not constructed successfully.
• D bulb 120 W Fusion lump
• Comparison Example T-5 The same procedure was employed as Example 1 except using H-2 for H-I .
• this transferable AR material and commercial acrylic board with 7 cm square and 2 mm thickness were put together and were inserted into a heat-press machine with two metal plates and heat-pressed for 40 seconds with 30 MPa pressure.
• the temperatures of the plates were 180 0 C for film/acrylic side and 50°C for the opposite side.
• the pressed materials were taken out and PET film was removed after cooling. As a result, the anti-reflection layer was successfully transferred on the acrylic surface.
• Comparison Example T-6 Commercial acrylic sheet with 2 mm thickness was used without any treatment.
• Spectral A black PVC sheet was put on the opposite side of the antireflection treatment by PSA and spectral reflectance at 580 nm was measured by spectrometer, F-20 (Filmetrics). For this measurement, a measurement position, where minimum reflection is located in 580 nm, were selected and used. (For blank acrylic sheet in comparison Example 6, reflectance at 580 nm was measured.)
• Scratch resistance Very fine steel wool (#0000 steel wool) was used to test a sample of the antireflection film. Samples were tested using 10 cycles of rubbing with a 400 gf/cm2 load. The samples were evaluated by naked eye observation to determine the number of scratches observed. 0 scratches indicates ideal performance, while acceptable performance is generally indicated for surface having a small portion of visible observed scratches.
• Transfer performance Transfer performance was evaluated by naked eye observation.
• Table II illustrates how the low refractive index composition (L-I) for use in the transferable antireflection material showed good reflectance, scratch resistance and transfer performance as compared with other samples.
• Table 1 also illustrates the preferred factors for high refractive index composition to achieve good results. Table 1 thus shows that the preferred low refractive index and high index composition is available for use in a transferable antireflection coating.

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